That's a good tip. Another way is:
1. Fill it with water.
2. Begin adding Nestea Instant Ice Tea mix. Be sure to keep track of how much you add!
3. Each time you add some, stir it together and taste.
4. Continue until it tastes correct.
Once this happens, compare your numbers (of how much tea you added) against the flavor chart on the back of the Nestea container to figure out how much water is needed for that amount of mix. You will now have the volume of your enclosure.
5. Drink the tea.

Comment

That's a good tip. Another way is:
1. Fill it with water.
2. Begin adding Nestea Instant Ice Tea mix. Be sure to keep track of how much you add!
3. Each time you add some, stir it together and taste.
4. Continue until it tastes correct.
Once this happens, compare your numbers (of how much tea you added) against the flavor chart on the back of the Nestea container to figure out how much water is needed for that amount of mix. You will now have the volume of your enclosure.
5. Drink the tea.

The packing peanuts sure. Water, sure... never heard of anyone using tea or coco mix to figure out how much water though.

If you fill with it liquid you could just measure the difference in weight then do some simple math, figure out how much weight of liquid (water most likely) is in it, then do more math to convert it to volume.

You could also remove the water out of the enclosure and then measure it in measuring cups or something.